Some design aspects of mobile local positioning systems

Aim: The aim of the present study was to determine the validity of position, distance traveled and instantaneous speed of team sport players as measured by a commercially available local positioning system (LPS) during indoor use. In addition, the study investigated how the placement of the field of play relative to the anchor nodes and walls of the building affected the validity of the system.Method: The LPS (Catapult ClearSky T6, Catapult Sports, Australia) and the reference system [Qualisys Oqus, Qualisys AB, Sweden, (infra-red camera system)] were installed around the field of play to capture the athletes' motion. Athletes completed five tasks, all designed to imitate team-sports movements. The same protocol was completed in two sessions, one with an assumed optimal geometrical setup of the LPS (optimal condition), and once with a sub-optimal geometrical setup of the LPS (sub-optimal condition). Raw two-dimensional position data were extracted from both the LPS and the reference system for accuracy assessment. Position, distance and speed were compared.Results: The mean difference between the LPS and reference system for all position estimations was 0.21 ± 0.13 m (n = 30,166) in the optimal setup, and 1.79 ± 7.61 m (n = 22,799) in the sub-optimal setup. The average difference in distance was below 2% for all tasks in the optimal condition, while it was below 30% in the sub-optimal condition. Instantaneous speed showed the largest differences between the LPS and reference system of all variables, both in the optimal (≥35%) and sub-optimal condition (≥74%). The differences between the LPS and reference system in instantaneous speed were speed dependent, showing increased differences with increasing speed.Discussion: Measures of position, distance, and average speed from the LPS show low errors, and can be used confidently in time-motion analyses for indoor team sports. The calculation of instantaneous speed from LPS raw data is not valid. To enhance instantaneous speed calculation the application of appropriate filtering techniques to enhance the validity of such data should be investigated. For all measures, the placement of anchor nodes and the field of play relative to the walls of the building influence LPS output to a large degree.

This paper presents an extensive local ultrasonic positioning system for mobile robots (MRs) based on the fusion of the information from the MR internal odometer sensor and the measurements of position obtained with a set of external ultrasonic beacons that form an Ultrasonic Local Positioning System (ULPS). The extensive ULPS is formed using several single ULPS, each one of them covering a particular area of the total working area. In each single ULPS, five ultrasonic beacons are used that emit simultaneously and are detected by an ultrasonic receiver on board the MR. Direct Sequence Code Division Multiple Access (DS-CDMA) techniques have been used to avoid interferences between them. When the MR navigates on the working area, it continuously obtains its relative position thanks to the internal odometer. The cumulative errors of the odometer are corrected when the robot is on a place where the positioning data obtained with any of the single ULPS are available. The fusion of information (from odometer and ULPS) is made using an H-Infinite filter. The extensive ULPS has been built and tested experimentally.

1. Abstract The marine science and technology area is characterized by a continually increasing number of users who require position location with varying degrees of accuracy and frequency. These users include (but are not restricted to):commercial ships (for navigation aid, harbor traffic control, search and rescue, and offshore drilling);unmoored buoys (for correlation of collected data and position information in order to develop environmental profiles); andunmanned instrumentation at offshore locations (for survey purposes). The required accuracies range from a few feet for survey applications to one and one-half miles or more for commerical ship navigation, and frequencies of position finding from almost continuously to once a day or more are needed. This paper treats the design and position accuracy analysis of a promising satellite-based position location system which can satisfy, in an economical fashion, the performance requirements of the various marine science and technology users. Position location is carried out by means of a single satellite employing an original range and range rate measurement method. Active participation of satellite ground control station, satellite, and user is required. The system design was executed under the important practical constraint of simple measurement instrumentation at the user in order to minimize the per unit user investment. The material in the paper is divided into four sections:description of position location system and the role of ground station, satellite, and user in the position determination procedure;probabilistic analysis of position location accuracy with emphasis of evolution of criteria for instrumentation measurement accuracy;design of measurement instrumentation with emphasis on user equipment; andapplications to marine science and technology users. Two new analytical techniques, developed specifically for the study of the range and range rate problem but applicable to position location systems in general, will be emphasized. Briefly, these techniques deal with:the notion of "distribution-free" accuracy for evaluating position accuracy in situations where the error distribution is unknown; andthe inclusion and statistical treatment of bias errors in the probabilistic analysis of position accuracy. II. Description of the Range and Range Rate Position Location System All position location systems can be unified in terms of the geometry of quadric surfaces, i.e., three-dimensional surfaces. Measurements are made which determine -distance and/or angle variables. These measurements are relative to positions or orientations either known or determined by other measurements. Each variable generates a quadric surface on which the measurement-determined position is located. An example of a quadric surface is the sphere generated by the measurement determined range between a user-and a satellite. Solution of the equations of three quadric surfaces yields the position (in general the solution yields a number of positions and the ambiguities must be resolved). A spherical or ellipsoidal approximation to the Earth's figure is often used as one of the surfaces (suitably extended to take into account user altitude above mean sea level). The position location concept considered in this paper is based on the measurement of the range and range rate between a single satellite and the user as well as a knowledge of user altitude and velocity and satellite position and

A method of mobile position tracking and velocity estimation for network-based mobile positioning systems is presented. Kalman filtering is used to process the sequences of mobile location measures obtained from time-of-arrival (TOA) geometric location techniques. Two-dimensional position tracking and velocity estimation are obtained. Simulation results show that carefully adjusting the processing rate of Kalman filtering can reduce the location tracking error. One post-Kalman-filter smoothing method is also proposed for better performance of velocity estimation.

The position location systems have become a hot issue over the past few years in wireless communication. So far, many people have thought of the Global Positioning System (GPS) as a position location system. But we can use the code division multiple access (CDMA) networks for position location. Two systems considered for position location in CDMA networks are direction finding and ranging. In this paper, we have examined the two systems and analyzed their performance. We also propose a position location system to mitigate the non-line of sight (NLOS) propagation error in IS-95 CDMA networks. We show that the proposed position location system improves the performance for the NLOS ranging error.

Location-aware software has become widespread outdoors. Indoor applications are now on the rise. However, careful selection of the appropriate local positioning system (LPS) and application fine-tuning are required in order to guarantee acceptable user experience. We present a simulation-based approach that includes application characteristics, LPS characteristics, and building characteristics to this complex task and illustrate how the appropriate LPS can be chosen and how applications can be fine-tuned. A sophisticated indoor navigation system is used as sample application. The paper also provides insights into subtle details and caveats of different LPS technologies from an application and building viewpoint.

Traditionally, localization systems for formation-keeping have required external references to a world frame, such as GPS or motion capture. Humans wishing to maintain formations with each other use visual line-of-sight, which is not possible in cluttered environments that may block their view. Our Local Positioning System (LPS) is based on ultra-wideband ranging devices and it enables teams of robots and humans to know their relative locations without line-of-sight. This demonstration shows live (real-time) local positioning between three agents (human and robot). The emphasis of this demonstration is showing the wearable interactive display that allows the human to see the local frame formation of the human and the robots.

The aim of this study was the validation of player and ball position measurements of Kinexon’s local positioning system (LPS) in handball and football. Eight athletes conducted a sport-specific course (SSC) and small sided football games (SSG), simultaneously tracked by the LPS and an infrared camera-based motion capture system as reference system. Furthermore, football shots and handball throws were performed to evaluate ball tracking. The position root mean square error (RMSE) for player tracking was 9 cm for SSCs, the instantaneous peak speed showed a percentage deviation from the reference system of 0.7–1.7% for different exercises. The RMSE for SSGs was 8 cm. Covered distance was overestimated by 0.6% in SSCs and 1.0% in SSGs. The 2D RMSE of ball tracking was 15 cm in SSGs, 3D position errors of shot and throw impact locations were 17 cm and 21 cm. The methodology for the validation of a system’s accuracy in sports tracking requires extensive attention, especially in settings covering both, player and ball measurements. Most tracking errors for player tracking were smaller or in line with errors found for comparable systems in the literature. Ball tracking showed a larger error than player tracking. Here, the influence of the positioning of the sensor must be further reviewed. In total, the accuracy of Kinexon’s LPS has proven to represent the current state of the art for player and ball position detection in team sports.

This paper presents a high-accuracy local positioning system (LPS) for an autonomous robotic greens mower. The LPS uses a sensor tower mounted on top of the robot and four active beacons surrounding a target area. The proposed LPS concurrently determines robot location using a lateration technique and calculates orientation using angle measurements. To perform localization, the sensor tower emits an ultrasonic pulse that is received by the beacons. The time of arrival is measured by each beacon and transmitted back to the sensor tower. To determine the robot's orientation, the sensor tower has a circular receiver array that detects infrared signals emitted by each beacon. Using the direction and strength of the received infrared signals, the relative angles to each beacon are obtained and the robot orientation can be determined. Experimental data show that the LPS achieves a position accuracy of 3.1 cm RMS, and an orientation accuracy of 0.23° RMS. Several prototype robotic mowers utilizing the proposed LPS have been deployed for field testing, and the mowing results are comparable to an experienced professional human worker.

This paper presents a feasibility study that deals with a local positioning system for a loader crane based on battery-powered wireless sensors and consists of two joint angular sensors and one telescopic boom length ranger. The practical challenges associated with using conventional sensors are described in order to provide the motivation behind the choice to use the sensing methods proposed in this paper. A novel method is tested using microelectromechanical system inertial sensors mounted around the crane joints to indirectly measure the joint angles, as well as an ultrasound time-of-flight ranging method to measure the telescopic boom length. The local positioning system's wireless sensor prototype designs are described in detail. Data from the angular sensor experiments conducted on a loader crane and the ultrasound ranging experiments conducted both in the laboratory and on the loader crane are presented and analyzed. The preliminary results from these experiments show that the performance of the new sensors is promising. The conclusion is drawn from the experimental results, and future work for this local positioning system is also described.

We have developed a DOA-based local area positioning system for position measurement of autonomous sweeping robot“SuiPPi”. This system can reduce the cost of the positioning system because it consists of a few components such as beacons, an array antenna and a signal processing unit. We have gotten the same accuracy as that of conventional TDOA system using wireless LAN. If beacons are placed at intervals of 20 [m], we can provide a positioning information of the robot in the accuracy of about 2 [m] .

Navigation and positioning system plays an important role in autonomous driving vehicles. In view of the existing problems, this paper mainly introduces the design and the implementation of local navigation and positioning system of UGVs. At first, this paper introduces all kinds of dead-reckoning algorithms for local navigation and positioning system of UGVs, including DR algorithm based on odometer, IMU, and the combination of IMU and odometer. Then, it analyzes the advantages, disadvantages and existing problems of these algorithms, and demonstrates the rationality of DR algorithm based on IMU and odometer. Finally, the navigation and positioning results of different algorithms are compared by experiments. Experiments show that the algorithm based on IMU and odometer is better than other algorithms. It is feasible to use to complete local navigation and positioning system of UGVs.

The autonomous driving of robots requires precise and reliable positioning information with low-cost sensors. In this paper, we propose a tightly coupled sensor fusion of multiple complementary sensors including GNSS-RTK, INS, odometry, Local Positioning System (LPS) and Visual Positioning. The focus of this paper is on the integration of LPS and vision since the coupling of GNSS-RTK, INS and odometry is already state of the art. We include the positions of the LPS anchors and the bearing vectors and distances from the robot’s camera towards the patch features as state vectors in our Kalman filter, and show the achievable positioning accuracies.

Background and aimsSoccer players frequently perform change-of-directions (CODs) at various speeds during matches. However, tracking systems have shown limitations to measure these efforts. Therefore, the aim of the present study was to propose a new approach to measure CODs using a local positioning system (LPS), and clarify position-related difference in profile of CODs by using the approach.MethodsThe x- and y-coordinate data for each soccer player were measured with a local positioning system. Speed, acceleration, jerk, and direction of speed were derived from the coordinate data. Based on accelerations of above 2 m/s2, the onsets and ends of CODs derived from jerk were identified (COD duration). Changes of direction of speed (θCOD) were determined for the corresponding period. Six collegiate male soccer players performed CODs according to 13 set angles (0–180°; every 15°) so that differences between θCOD and set angle could be determined (Exp. 1). Relative frequency distributions of θCOD and number of CODs were determined in 79 collegiate and amateur male soccer players during 9 soccer matches (Exp. 2).ResultsIn Exp. 1, θCOD was positively related to set angle (r = 0.99). Each θCOD was smaller than the corresponding set angle, and the difference became greater with increasing COD angle. In Exp. 2, The number of CODs in a match was 183 ± 39 across all positions. There were no significant position-related differences in the number of CODs. The duration of a COD was 0.89 ± 0.49 s across all positions. The relative frequency distribution of θCOD revealed that the number of CODs at 0–15° and 105–135° tended to be higher than those at other angles during soccer matches. Further, θCOD was affected by the speed at the onset of COD during soccer matches (Exp. 2).ConclusionsThe current findings demonstrate that θCOD derived from direction of speed and jerk may be a new indicator for evaluating COD during soccer matches.

Beach handball is a young discipline that is characterized by numerous high-intensity actions. By following up on previous work, the objective was to perform in-depth analyses evaluating external load (e.g., distance traveled, velocity, changes in direction, etc.) in beach handball players. In cross-sectional analyses, data of 69 players belonging to the German national or prospective team were analyzed during official tournaments using a local positioning system (10 Hz) and inertial measurement units (100 Hz). Statistical analyses comprised the comparison of the first and second set and the effects of age and sex (female adolescents vs. male adolescents vs. male adults) and playing position (goalkeepers, defenders, wings, specialists, and pivots) on external load measures. We found evidence for reduced external workload during the second set of the matches (p = 0.005, ηp2 = 0.09), as indicated by a significantly lower player load per minute and number of changes in direction. Age/sex (p < 0.001, ηp2 = 0.22) and playing position (p < 0.001, ηp2 = 0.29) also had significant effects on external load. The present data comprehensively describe and analyze important external load measures in a sample of high-performing beach handball players, providing valuable information to practitioners and coaches aiming at improving athletic performance in this new sport.